The video packets consist in the generation, during the coding of each image of the video, of binary data that are spatially independent of one another. The binary train of an image consists of several packets, isolated from one another by resynchronization markers. Each packet can be tagged by the synchronization marker which precedes it. It can be decoded without knowing the data of the neighbouring packets. This tool ensures more robustness to decoding in the event of loss of packets since these losses do not give rise to spatial propagation of errors.
The cost of compression of the video data is generally dependent on the quality of the image desired on reception. This relation is known and depends mainly on the value of the quantization interval of the DCT coefficients. Conventionally, compression is improved by implementing effective coding strategies utilizing all the options offered by the coding scheme. These strategies relate essentially to the following two points:                choice of the modes of image coding, macroblock and block, ensuring a satisfactory compromise between coding quality and coding cost in these modes;        for the temporally predicted images, choice of the motion vectors ensuring a satisfactory compromise between quality of the temporal prediction and cost of coding of the vectors.        
Although these coding procedures, in general defined in the standards, are very effective, it is beneficial to implement additional means of reducing coding cost, the costs of transmission or of bandwidth remaining a major problem. It is in fact a matter of finding a compromise between the conventional compression procedures such as increasing the quantization interval and new procedures, to obtain a better image quality/coding cost ratio.